Chamberlain was naive, I think, when it came to Hitler. He wasn't just stalling - he genuinely hoped Hitler would prove to be willing to turn away from aggression. But he wasn't so naive as to put all his hopes into that. He hoped to avoid war, but knew he might not be able to - and so he supported preparations to deal with that eventuality. To me, the most compelling evidence in his favour is that when he was forced to retire on the grounds of ill health in mid 1940 (he had cancer and he wouldn't survive the year), Winston Churchill tried to persuade him to accept Britain's highest order of Chivalry - as a Knight of the Garter. Churchill felt that Chamberlain was worthy of that. In his writings, Churchill condemned many of the choices Chamberlain made, and with justification at times - but he still saw a man who had given his best and his all for his country. And had done well enough.
Allowing millions of people to be taken over by the Nazi's?
It was Churchill that pressed for rearmament and constantly warned about the Nazi threat, while Chamberlain lived in his own fantasy world of the League of Nations.